Dipole Moment Effect of Cyano-Substituted. Transistor Memory

Transcription

1 Dipole Moment Effect of Cyano-Substituted Spirofluorenes on Charge Storage for Organic Transistor Memory Chen Sun,, a Zongqiong Lin,, a Wenjuan Xu, Linghai Xie,* Haifeng Ling, Mingyang Chen, Jin Wang, Ying Wei, Mingdong Yi,* Wei Huang*, Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials(IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing , China. Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing , China. Chemicals and Materials. All the solvents and reagents were purchased from commercial suppliers and used without further purification, unless noted otherwise. All products were purchased by flash column chromatography which was carried out with Kanto Silica Gel 60N (40-63 µm). Spectrochemicalgrade solvents were used for optical measurements. Dichlorobis(triphenylphosphine) palladium(ii), and n-butyllithium were obtained from Aldrich Chemical Co. Sulfuric acids, nitric 1

2 acid, bromine, sulfur monochloride, N,N-dimethyl formamide, aliquat 336, potassium carbonate, magnesium sulphate, chloroform, and toluene were purchased from Sinopharm Chemical Reagent Co., LtdS without further purification. THF and toluene were dried over sodium benzophenone ketyl anion radical and distilled under a dry nitrogen atmosphere immediately prior to use. 2,7-dibromo-9,9-dioctyl-fluorene, 2,7-bis(1',3',2'-dioxaborolan-2'-yl)-9,9'-dioctylfluorene, 2-bromo-9,9-dioctyl-fluorene, 2,7- dibromo- 4,5- diazafluoren- 9-one, 2-boromo-4,5- diazafluoren-9-one were obtained according to the literatures. Characterization. 1 H-NMR and 13 C-NMR were recorded on a Bruker 400 MHz spectrometer in d-cdcl 3 with tetramethylsilane (TMS) as the interval standard. Mass spectra were recorded on a Shimadzu GCMS 2010 PLUS. Element analyses were carried out on an Elementa Analysensysteme GmbH Vario EL III Instrument. Absorption spectra were measured with ashimadzu UV-3150 spectrometer at 25, and emission spectra were recorded on a Shimadzu RF-530XPC luminescence spectrometer upon excitation at the absorption maxima. Cyclic Voltammetric (CV) studies were conducted at room temperature on the CHI660E system in a typical three-electrode cell with a platinum sheet working electrode, a platinum wire counter electrode, and a silver/silver nitrate (Ag/Ag+) reference electrode. All electrochemical experiments were carried out under a nitrogen atmosphere at room temperature in an electrolyte solution of 0.1 M tetrabutylammonium hexafluorophosphate (Bu 4 NPF 6 ) in CH 2 Cl 2 at a sweeping rate of 0.1 V/s. According to the redox onset potentials of the CV measurements, the highest occupied molecular orbital (HOMO)/lowest unoccupied energy levels (LUMO) of the materials are estimated based on the reference energy level of ferrocene (4.8 ev below the vacuum): HOMO/LUMO = (Eonset 0.04 V) 4.8 ev, where the value 0.04 V is for ferrocene vs Ag/Ag+. 2

3 Fabrication of pentacene-based transistor memory devices. The schematic configuration of the fabricated pentacene-based OFET memory devices is shown in Figure 1b. Highly doped n-type Si(100) wafer was used as the substrate. A 300 nm thick SiO 2 layer as a gate dielectric was thermally grown onto the Si substrates. The substrate was rinsed with toluene, acetone, isopropyl alcohol and dried with a steam of nitrogen. The SFX, CNSFX and DCNSFX were thermally deposited under vacuum ( torr) on the Si/SiO 2 substrate with a deposition rate of 0. 4 Hz s -1 at 59.5, 75.5 and 98.6 C respectively. The thicknesses of prepared SFXs films were estimated around 5 nm 1. A toluene solution of 10% SFXs blended in PS (5 mg/ml) was stirred overnight to form a homogeneous solution. Thereafter, the solution was filtered through a 0.22 mm pore size PTFE membrane syringe filter and spin-coating at 3000 r/min for 30 s onto the wafer substrate. The mixed thin film was dried under vacuum (10-4 torr) at 80 C for 0.5 h to remove residual solvents. The thicknesses of the prepared thin film were estimated to be around 30 nm. The thicknesses of the films are measured by Bruker Dektak XT stylus profiler. The pentacene was thermally deposited with a deposition rate of nm s -1 at C under vacuum ( torr) to form a 40 nm thick film. A 25.5 nm thick gold electrode was subsequently deposited by thermal deposition through a shadow mask under vacuum ( torr). The channel length (L) and width (W) of the devices were 50 and 1000 mm, respectively. Theoretical computation methods. 3

4 The Density Functional Theory (DFT)/B3LYP/6-31G calculations of the excitation energies were then performed at the optimized geometries. All the quantum-chemical calculations were performed using the Gaussian09 suite of programs. Preparation of spiro[fluorene-9,9'-xanthene]-2-carbonitrile (CNSFX). In a two-necked flask (150 ml), 2-BrSFX (0.5g, 1.22 mmol, 1.0 equiv), K 4 [Fe(CN) 6 ].3H 2 O (0.63g, 1.22 mmol, 1.0 equiv), sodium carbonate (2.11g, 1.22 mmol, 1.0 equiv), and Pd(OAc) 2 ( mol %) were added. The flask was evacuated and back-filled with nitrogen atmosphere over three times, after which DMF (10 ml) were injected into the flask through syringe. The mixture was heated up to 160 C and refluxed for 24 h. Upon completion, the reaction mixture was cooled to rt and diluted with 20 ml of DCM. The resulting slurry was filtered and the filtrate assayed for content. The product can be isolated by washing the filtrate with water (2 15 ml) and 5% NH 4 OH (1 15 ml). The combined organic layer was dried over anhydrous Na 2 SO 4, filtered and evaporated to dryness. The crude product was purified by silica gel column chromatography using petroleum ether/dichloromethane mixed solvent as eluent affording 4.25 g (85 %) of a yellow solid. 1 H NMR (400 MHz, d-cdcl 3, ppm) δ (d, J = 10.4 Hz, 2H), (d, J = 9.2 Hz, 1H), (t, J = 15.2 Hz, 1H), 7.43 (s, 1H), (t, J = 16.0 Hz, 1H), (m, 5H), (t, J = 16.4 Hz, 2H), (d, J = 16.4 Hz, 2H). 13 C NMR (100 MHz, d-cdcl 3, ppm) δ , , , , , , , , , , , , , , , , , , , GC-MS (m/z): calcd for C 26 H 15 NO , found 457 (100%). Anal. calcd for C 26 H 15 NO: C, 87.37%; H, 4.23%; N, 3.92%; O, 4.48%. found: C, 84.90%; H, 3.64%; N, 7.30%; O, 4.16%. Preparation of spiro[fluorene-9,9'-xanthene]-2,7-dicarbonitrile DCNSFX. 4

5 The process was the same with the preparation of CNSFX. As a white powder DCNSFX (2.94 g, 75%) was obtained. 1 H NMR (400 MHz, d-cdcl 3, ppm) δ (d, J = 8 Hz, 2H), (d, J = 8 Hz, 2H), 7.49 (s, 2H), (m, 4H), (m, 2H), (d, J = 8 Hz, 2H). 13 C NMR (100 MHz, d-cdcl 3, ppm) δ , , , , , , , , , , , , , GC-MS (m/z): calcd for C 27 H 14 N 2 O , found 382 (100%). Anal. calcd for C 27 H 14 N 2 O: C, 84.80%; H, 3.69%; N, 7.33%; O, 4.18%. found: C, 84.92%; H, 3.63%; N, 7.30%; O, 4.15%. 5

6 Figure S1. 1 H-NMR and 13 C-NMR spectra of CNSFX in CDCl 3. 6

7 Figure S2. 1 H-NMR and 13 C-NMR spectra of DCNSFX in CDCl 3. Figure S3. Cyclic voltammogram of the reduction in THF solution and the oxidation in CH 2 Cl 2 solution for SFX, CNSFX and DCNSFX. 7

8 Figure S4. UV-vis absorption of SFX, CNSFX and DCNSFX in diluted dichloromethane solution and films evaporating under vacuum on quartz substrate 8

9 Figure S5. PL spectra of SFX, CNSFX and DCNSFX in diluted dichloromethane solution and films evaporating under vacuum on quartz substrate. Figure S6. Output characteristics of transistor memory devices based on SFX. 9

10 Figure S7. Output characteristics of transistor memory devices based on CNSFX. Figure S8. Output characteristics of transistor memory devices based on CNSFX. 10

11 Figure S9. Stepwise negative shifts of transfer curve with increasing the negative gate bias on SFX based device. The black arrow the shift direction of transfer curves. Figure S10. Stepwise negative shifts of transfer curve with increasing the negative gate bias on CNSFX based device. The black arrow remark the shift direction of transfer curves. 11

12 Figure S11. Stepwise negative shifts of transfer curve with increasing the negative gate bias on DCNSFX based device. The black arrow remarks the shift direction of transfer curves. Figure 12. The schematic diagram of non-electrical-erasing (a) and photo-erasing (b) progress for SFXs based transistors. 12

13 Figure S13. Reversible current response to the WRER cycles of SFX based transistors. The currents at ON and OFF states were read at V g = -30 V and V d = 30 V. Figure S14. Reversible current response to the WRER cycles of CNSFX based transistors. The currents at ON and OFF states were read at V g = -30 V and V d = 30 V. 13

14 Figure S15. Reversible current response to the WRER cycles of DCNSFX based transistors. The currents at ON and OFF states were read at V g = -30 V and V d = 30 V. Figure S16. Retention test of multi-bit storage with 3 levels for SFX based transistor. 14

15 Figure S17. Retention test of multi-bit storage with 3 levels for CNSFX based transistor. Figure S18. The V th, charge density and charge trapping rate as the function of programming time (t Prog. ) in the SFX based transistor. 15

16 Figure S19. The V th, charge density and charge trapping rate as the function of programming time (t Prog. ) in the CNSFX based transistor. Figure S20. Output characteristics of transistor memory devices based on SFX blended in PS. 16

17 Figure S21. Output characteristics of transistor memory devices based on CNSFX blended in PS. Figure S22. Output characteristics of transistor memory devices based on DCNSFX blended in PS. 17

18 Figure S23. Transfer characteristic of the transistor before and after gate bias in dark with SFX blended in PS. The drain current was measured at V ds = -50 V. The programming bias (VP rog. ) was -160 V and programming time (t Prog. ) was 20 ms. Figure S24. Transfer characteristic of the transistor before and after gate bias in dark with CNSFX blended in PS. The drain current was measured at V ds = -50 V. The programming bias (VP rog. ) was -160 V and programming time (t Prog. ) was 20 ms. 18

19 Figure S25. AFM topographic images of SFX (a), CNSFX (b) and DCNSFX (c) blended in PS films on SiO 2 /Si substrates. Figure S26. AFM topographic images of pentacene on different surfaces: (d) SFX, (e) CNSFX, (f) DCNSFX blended in PS modified SiO 2 surface. 19

20 Figure 27. Reversible current response to the WRER cycles of SFX blended with PS based transistors. The currents at ON and OFF states were read at V g = -30 V and V d = 30 V. Figure 28. Reversible current response to the WRER cycles of CNSFX blended with PS based transistors. The currents at ON and OFF states were read at V g = -30 V and V d = 30 V. 20

21 Figure S29. Retention test for SFX blended in PS based transistor. Figure S30. Retention test for CNSFX blended in PS based transistor. REFERENCES (1) Hinsberg, W.D.; Willson, C.G.; Kanazawa, K.K. Measurement of Thin-Film Dissolution Kinetics Using a Quartz Crystal Microbalance. J. Electrochem. Soc. 1986, 133,